Metallurgical process



W. E. GREENAW'ALT.

METALLURGICAL PROCESS- APPLICATION FILED NOV. 28, 1917.

1 ,344, 1 27. Patented June 22, 1920.

Thiclzerzed pulp (Solution Residua v10 4m Can cerzZ/uzlar VWmwszsz-s WILLIAM E. GREEHAWALT, OF DENVER, COLORADO.

METALLURGICAL rnocnss.

Specification of Letters Patent.

Patented June 22, 1920.

Application filed November 28, 1917. Serial No. 204,337.

To all whom it may concern:

Be it known that I, WILLIAM E. GREENA- WALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented certain new and useful Improvements in Metallurgical Processes, of which the following is a specification.

My invention relates to electrolytic and flotation processes of treating ore of metals. It has for its moreimmediate object the treatment of mixed sulfid and oxid ores, especially of copper, although it is not intended to limit it to any particular ore or to any particular combination of minerals in the ore.

It is well known that oxidized ores of copper are not ordinarily amenable to flotation, and that it has been quite a problem to successfully float either oxidized ore, or sulfid ores containing some oxids.

A common method of procedure in flotation is, to add acid to the ore pulp: the acid so added is supposed to help float the mineral, butit is too small in amount to exert any solvent action on the mineral content of the ore, and so far as known, none is claimed. In this process it is intended to add sufficient acid, say, to mixed sulfld and oxid ores of copper, to exert a solvent action on the oxids, and then electrolyze the resulting metal solution in such a way that the electrolytically separated metal is floated, together with the sulfid minerals.

In describing the process more in detail, it may be assumed that the ore under treatment is a mixed sulfid and oxid ore of copper, which is quite common, and which occurs in large deposits in the western part of the United States. The sulfid mineral is usually in the form of chalcocite and chalcopyrite, and the oxid mineral usually in the form of malachite, azurite, and melaconite. All the oxid and carbonate ores of copper are easily attacked by all mineral acids. Sulfuric acid, being the most 'common, will be supposed as being used in the present description.

The ore, usually finely pulverized, is treated with a dilute solution of sulfuric acid. This attacks the oxids, and the copper goes into solution as the sulfate. The acid pulp, in which the sulfids are pract1- cally unaffected and the oxids partially or totally converted into the sulfate, is agltated with flotation oils, and the mixture ingenerated which will immediately dissolve more copper, ferric salts are formed which are immediately reduced by the action of the minerals in the pulp, and gases such as oxygen and hydrogen are liberated which will float, or materially assist in the flotation of, both the mineral and the metal.

Sponge copper, deposited with a high current density, may float without the assistance of ordinary flotation agents. This is probably due to occluded hydrogen. It is easily floated with the assistance of flotation agents.

'VVhile any suitable apparatus may be used, an apparatus, such 'as shown in diagrammatic section in the accompanying drawing, will be found convenient for carrying out the process.

In the drawing, 1 is a flotation tank containing electrodes 2 and 3, for electrolyzing the ore pulp. Suspended vertically within the tank is a shaft 4:, at the upper end of which is attached a pulp distributor 6, and at the lower end an agitator 5. The shaft is rotated by the motor 7. 10 is a thickener, or separator, for separating the liquid from the solids after treatment. 13 is a pump to elevate the liquid from the overflow launder 12 to the agitating tank 15. 17 is another thickener, for the finely ground ore pulp, by means of which the water used in grinding is separated from the solids, and the water returned to the grinding mill 19, while the thickened solids flow into tank 15 for acid treatment and mixing of the flotation agent.

In operating the process, the thickened pulp from the mill 19. is flowed into tank 15, where it is treated with acid and oil,'so that much of the soluble copper is brought into solution and the pulp mixed with the flotation agent. The pulp then flows into the combined flotation and electrolytic cell 1, distributed by the distributer 6. The electric current in the cell, which is preferably of a high current density, loosely deposits the copper on the cathodes, while oxygen is liberated at the anodes. Sulfuric acid and ferric sulfate are also produced. Hydrogen may also be liberated at the cathodes. The liberated gases float the sulfid minerals, as also the sponge copper deposited on the cathodes, as rapidly as it becomes detached. The acid and ferric salts regenerated in the pulp dissolve more copper, which is in turn deposited. The deleterious action of the ferric salts, so highly injurious in ordinary electrolys1s of impure copper solutions, is

. overcome by both the high current density and by the oXid and sulfld minerals in the pulp. The stirrer 5, acts to distribute the released gases of electrolysis and give them uniformity of action, and to loosen the deposited copper from the cathodes. It also serves to distribute extraneously introduced gases through the pipe 24, if such gases are desired.

The pulp, now. having both the combined and elemental copper largely removed by flotation and electrolysis, is collected in the and thus the process goes on indefinitely.-

The gangue, separated from most of the liquid used in the electrolysis and flotation, flows out of the separator 10, by the outlet 11, over a gravity concentrator 22, where any of the mineral or electrolytically deposited metal which was too heavy to float, is separated from the gangue by gravity concentration, by any of the well known devices. The small amount of copper sulfate which escaped electrolysis and recovery in the separator 10, may be chemically precipitated if found worth while. The flotation concentrate in the cell 1, overflows into the launder 21, and is removed as desired.

It is usually desirable to crush wet: the ore may be crushed in the usual way with the usual amount of water, and then most of the water removed from the solids in the thickener 17, and returned to the mill 19 to pass through another cycle, while the thickened pulp flows into the agitating tank 15 for treatment.

The pulp, treated with a flotation agent and a solvent for the copper in tank 15, is distributed over the electrodes in the cell 1, and passes in a downward stream between the electrodes against the current of ascending gases liberated by the electrolytic action,

their highest efliciency. Under the action of this process, not much gas is required.

It is advisable to retain as much of the solution from the separator 10, as possible, in the circuit, for, this solution not only acts as a solvent for the copper, but also as a conductor of the electric current in the electrolysis.

To the finely ground ore, in the agitator 15, will usually be added enough water and regenerated acid solution to make an easy flowing pulp-much the same as in ordinary flotation work;v that is to say, an amount of water equal to about four to six times the weight of the ore. It is preferred to have the solution of the copper, in the agitator 15, go on continuously, and the rate of flow arranged so that about one-fourth of the copper is brought into solution before entering the electrolyzer 1, so that the remainder of the soluble copper can be acted upon by the acid and ferric salts regenerated by the electrolytic action. The time of treatment will depend almost entirely upon the nature of the ore and the strength of the acid. Usually, one hour will be sufficient time for acid treatment in the agitator 15, with a five per cent. acid solution. The strengthof the acid. will depend largely on the amount of soluble copper in the ore, and will usually vary from two to five per cent. Fresh acid may be added from time to time from the acid storage tank 25, as desired. The flotation agent may be added to the agitator 15, from the flotation agent tank 26, or, added afterward to the stream of pulp flowing from the agitator to the electrolyzer. The nature and the amount of flotation agent used, will depend on the nature of the ore, and will have to be determined much the same as in ordinary flotation work. It will usually vary from one-fourth to several per cent. of the weight of the dry ore.

The E. M. F. required will depend mostly on the amount of copper in the solution, the acidity of the solution, its temperature, and very largely on the current density. The current density will usually vary from fifty to one hundred ampheres per s uare foot; with such current densities the M. F. required will usually vary from three to five volts. The distance between the electrodes is about the same as in other copper deposition; that is to say, it will vary from one inch to two inches.

The relative amounts of oxid and sulfid minerals will depend, practically, entirely on the product from the mine. The limits will be determined mostly by economic considerations. If the ore is hi h in oxid minerals and low in sulfids, or, i the ore is composed entirely of oxid minerals, it would probably be better to filter the solutions before electrolyzing, as in ordinary solvent processes: if, however, filtering is diflicult, and the purity of the deposited copper immaterial, there still might be an advantage in using the present method. Ordinarily, it will find its best application in ores containing most of the values in the form of sulfids, and not suflicient oxids to warrant a separate solvent process.

A little experimenting will be necessary for each individual case, to deposit the copper in a non-adherent form on the cathode, so that the copper, as it becames detached, can be floated from the liquid. In this way the cathodes never need stripping, or removing, but are practically permanent until worn out. On the other hand, the copper so deposited and recovered, is very impure and needs additional refining, as compared with the pure electrolytic metal obtainable by the re ular electrolytic solvent processes.

claim:

1. A metallurgical process which consists in treating mixed sulfid and oxid ores of copper with a solvent for the oxidized copper, applying a flotation agent to the ore pulp, electrolyzing the ore pulp at a cur: rent density suflicientl high to give a loose deposit of copper, an floating the metallic copper produced by the'electrolysis and the sulfid mineral with gases liberated by the electrolytic action.-

2. A process which consists in treating mixed sulfid and oxid ores of copper with a solvent for the oxidized copper, applying a flotation agent to the ore pulp, electrolyzing the ore pulp at a current density sufliciently high to give a loose deposit of copper, and floating the metallic copper and the sulfid mineral from an electrolyzed pulp.

3. A metallurgical process which consists in treating ores of metals with a solvent for the metals, electrolyzing the resulting metal solutions in the presence of the g'angue to deposit the metal loosely upon the cathode and capable of being floated by the addition of flotation agents, and recovering the electrolytically loosely deposited metal from the liquid by flotation.

4. A metallurgical process which consists in treating ores of metals with a solvent for the metals, electrolyzing the resulting metal solution to deposit the metal loosely upon the cathode and capable of being floated by flotation agents, and recovering the loosely electrolytically deposited metal from the liquid by flotation.

5. A metallurgical process which consists in treating mixed sulfid and oxid ores of metals with a solvent for the metals, applying a flotation agent to the ore pulp, electrolyzing the pulp, and floating the resultingl electrolytic metal with the sulfid minera 6. A metallurgical process which consists in treating mixed sulfid and oxid ores of metals with a solvent for the metals, electrolyzing the resulting metal solution to de posit the metal upon the cathode in a form capable of being detached during the elec trolysis and capable of being floated by the addition of flotation agents, and recovering the electrolytically deposited metal with the sulfid mineral contained in the ore by flotation.

7. A metallurgical process which consists in treating ores of metals with solventfor the metals, electrolyzing the resultin metal solution with a current density su ciently high to give a spongy deposit and capable of detaching itself from the cathode and capable of belng floated on the addition of flotation agents, and recovering the metal so deposited by flotation.

8. A metallurgical process which consists in mixing finely ground ores of metals with asolvent for the metals and with a flotation agent, electrolyzing the ore pulp, agitating the pulp, and passing the stream of pulp against the ascending gases liberated by the electrolytic action.

9. A metallurgical process which consists in subjecting ores of metals to the action of an electric current in the presence of an acid solution to convert the metal constituents of the ore into the form of sponge metal capable of being floated on the addition of suitable flotation agents, and recovering the resulting metal from the li uid by flotation.

WILLI E. GREENAWALT. Witnesses:

MARY H. BRooKs, IRMA GREENAWALT.

electrolytically produced sponge 

